Liquid pumps are used in many applications, such as, for example, beverage dispensers commonly found in restaurants or cafes. After a user presses an appropriate button, inserts a correct amount of money, or otherwise interacts with the beverage dispenser, a pump mechanism within the beverage dispenser will dispense the beverage. As the functioning of the beverage dispenser is highly dependent upon the functioning state of the pump mechanism, it is desirable for the pump mechanism to be safe and reliable, and have a long operational life and efficient performance.
FIGS. 1A and 1B illustrate a liquid pump 100 used in the current art. Liquid pump 100 comprises a housing defining a pump chamber 102. An inlet 104 and an outlet 106 are located on opposite sides of the pump chamber 102. An output shaft 114 of a motor 112 extends through a through hole on a bottom wall 116 of pump chamber 102 to drive a drive gear 108 housed within pump chamber 102, wherein drive gear 108 is coupled to a driven gear 110 also contained within pump chamber 102. During pump operation, the rotation of drive gear 108 and driving gear 110 pumps fluid from inlet 104 to outlet 106 in a controlled manner.
A sealing member 118 disposed around output shaft 114 is located in a support base formed beneath bottom wall 116 of pump chamber 102, preventing leakage of liquid through gaps between output shaft 114 and the through hole on bottom wall 116.
An open end of pump chamber 102 is closed by an inner cover 120, which may be supported by shoulder portions 122 formed by the sidewalls of pump chamber 102. A sealing ring 124 is disposed between inner cover 120 and an outer cover 126. Pressure from outer cover 126 causes sealing ring 124 to exert a pressure on inner cover 120, causing inner cover 120 to maintain sliding contact with an axial surface of drive gear 108 and driven gear 110. In addition, sealing ring 124 and inner cover 120 form an interface with the side walls of pump chamber 102, preventing liquid in pump chamber 102 from leaking through inner cover 120.
During operation of pump 100, inner cover 120 rubs against the surface of drive gear 108 and driven gear 110, causing wear and tear. Continuous wear and tear may create a gap between inner cover 120 and the axial surfaces of drive and driven gears 108 and 110. In addition, the rotation of drive gear 108 and driven gear 110 causes the liquid within the pump chamber to be under high pressure, which exerts a force on inner cover 120 that may overcome the pressure exerted by sealing ring 124 and further increases the size of the gap, lowering the efficiency of pump 100.
Furthermore, during operation of pump 100, sealing member 118 is exposed directly to the high pressure from the liquid within pump chamber 102, causing greater wear and shorter operational life of sealing member 118, which decreases the operational life of pump 100 as a whole.
Accordingly, there exists a need for a liquid pump having a longer operational life and higher efficiency, addressing the problems described above.